1. Field of the Invention
The present invention relates to a method of manufacturing III-nitride semiconductor devices, especially to a method of reducing the specific contact resistance between metal and p-type III-nitride semiconductor devices.
2. Description of the Related Art
Since Nichia Company of Japan disclosed the technology of forming GaN epitaxy layer on Al2O3 (sapphire) substrate, III-nitride semiconductors have become more and more important and been considered as main material of blue light-emitting diodes, laser diodes and electronic devices. Nowadays one of the key factors that affects the lifetime of light-emitting diodes, laser diodes and electronic devices is ohmic contact between metal and p-type III-nitride semiconductors. Besides, in both of electronic devices and optoelectronic devices manufacturing process, it is a basic demand to form ohmic contact with low resistance between metal and p-type III-nitride semiconductors. The conventional methods for forming low specific contact resistance between metal and p-type GaN are as follows: (1) applying diffusion technology or ion implantation technology to p-type III-nitride semiconductor manufacturing process; (2) increasing doped concentration of magnesium in growing p-type III-nitride semiconductors; (3) evaporating a metal layer whose higher work function onto p-type III-nitride semiconductor surface; (4) processing p-type III-nitride semiconductors with various types of surface treatments, such as KOH, HCl, or aqua regia treatment, etc.
However, since the carrier concentration of p-type III-nitride semiconductors cannot be raised effectively and metal whose work function higher than p-type III-nitride semiconductors is absent, the conventional methods still fail to achieve a desired low specific contact resistance between metal and p-type III-nitride semiconductors.
Therefore, a method for lowering the specific contact resistance between metal and p-type III-nitride semiconductors is urgently required.
Therefore, one object of the invention is to provide a method for forming ohmic contact between metal and p-type III-nitride semiconductors.
Another object of the invention is to provide a method for manufacturing III-nitride semiconductor devices, which has a low specific contact resistance between metal and p-type III-nitride semiconductors.
According an embodiment of the invention, the method for forming ohmic contact between metal and p-type III-nitride semiconductors includes the steps of:
dipping samples formed with p-type III-nitride layer into ammonium sulfide solution to remove native oxide from the surface of said p-type III-nitride layer;
cleaning and drying the samples;
evaporating metal layer onto the surface of the p-type III-nitride layer; and
processing the samples with thermal alloy treatment.
According to another embodiment of the invention, the method for forming ohmic contact between metal and p-type III-nitride semiconductors includes the steps of:
performing oxidation treatment to samples formed with p-type III-nitride layer;
dipping the samples into ammonium sulfide solution to remove oxide from the surface of said p-type III-nitride layer;
cleaning and drying the samples;
evaporating metal layer onto the surface of the p-type III-nitride layer; and
processing the samples with thermal alloy treatment.
The objects, features and advantages of the present invention will become more apparent with reference to the accompanying drawings and the following detailed descriptions.